In conventional automotive alternator rotors, a rotor core includes: a cylindrical portion on which a field winding is installed with an insulating member interposed; yoke portions disposed so as to extend radially outward from each of two axial end portions of the cylindrical portion; and a plurality of claw-shaped magnetic poles bent so as to extend axially from outer peripheral portions of each of the yoke portions and intermesh with each other alternately so as to cover the field winding. A predetermined clearance is disposed between adjacent claw-shaped magnetic poles so as to prevent magnetic flux from leaking out from between the adjacent claw-shaped magnetic poles. In addition, ring-shaped vibration damping members are disposed so as to be placed in close contact with inner peripheral surfaces of the claw-shaped magnetic poles and an outer peripheral surface of the field winding. (See Patent Literature 1, for example.)
An automotive alternator having a Lundell rotor of this kind has a power generating function in which magnetic flux is generated by passing an electric current to the field winding and an alternating current flows through an armature winding due to changes in the magnetic flux arising together with rotation of the rotor.
Patent Literature 1: Japanese Patent Laid-Open No. HEI 4-325853 (Gazette)